1. Field of the Invention
The present invention relates to a retainer for holding, on a work-delivery box or palette, a produced photoreceptor drum or a base tube serving as its raw material, in a process for producing photoreceptor drums to be used in an image forming apparatus such as an electrophotographic copying apparatus, a printer, a facsimile or the like.
2. Description of Related Art
FIG. 1 is a flow chart or diagram schematically illustrating the steps of producing photoreceptor drums. First, a base tube 1 serving as a raw material of a photoreceptor drum is loaded in a production line. For example, the base tube 1 is obtained by machining an extruded base tube of aluminum of which diameter is about 60.about.300 mm and length is up to about 600 mm. At a high-pressure cleaning step, a detergent or the like under high pressure is sprayed to the outer and inner peripheral surfaces of the base tube 1 which is vertically moved while rotated. This removes dust and oil content stuck on the surfaces of the base tube 1.
At an ultrasonic cleaning step, the base tube 1 is subjected to ultrasonic cleaning in a detergent for degreasing. At a brush cleaning step, the outer peripheral surface of the base tube 1 is rubbed and cleaned with a rotary brush 2, thereby to remove firmly adhering foreign matter. Upon completion of degreasing and polishing by cleaning, a rinsing step is then conducted. More specifically, the base tube 1 is put in pure water into which clean air is blown to cause bubbling. With the use of bursting of air bubbles, the base tube 1 is rinsed. At a hot-water pulling step, the base tube 1 is slowly pulled up from pure water, which has been heated to decrease the viscosity. This drains water off from the surfaces of the base tube 1.
Upon completion of the cleaning steps above-mentioned, there is conducted a drying step where the adsorbed water on the surfaces of the base tube 1 is removed in an atmosphere of 130.about.140.degree. C. At a coating step, the base tube 1 with the upper end thereof hermetically sealed, is immersed, except for the upper end thereof, in a previously prepared solution of a photosensitive material which is circulated. Thus, the base tube 1 is coated at its outer peripheral surface with the photosensitive material. At a lower-end separating step, there is separated the photosensitive material coated to the outer and inner peripheral surfaces of the base tube 1 at its lower end.
At a thermal-treating step, the base tube 1 is gradually heated at a predetermined temperature gradient. Without so-called bubble defects produced, this removes the solvent in the coated photosensitive material and solidifies the photosensitive material.
The steps above-mentioned are conducted in a clean room.
At an inspection step, the base tube 1 is subjected to an appearance inspection. Then, at an assembling step, flanges are attached to the both ends of a photoreceptor drum thus produced. The photoreceptor drum thus assembled is then packed and stored.
A moving and placing machine is conventionally used to pick, move and place a base tube 1 (or a produced photoreceptor drum) from, to and on machines for conducting the steps above-mentioned.
FIG. 2 is a view schematically illustrating the arrangement of a chucking device of a moving and placing machine (not shown) for use in a production step. A chuck shaft 6 is fixed to a chuck-fixing unit 7 of the moving and placing machine movable vertically in the directions of arrows. A chuck 5 is secured to the lower end of the chuck shaft 6. The chuck 5 is arranged to pick a base tube 1. The chuck 5 is provided at the lower end thereof with a tapered guide 4 for guiding itself into a base tube 1. The base tube 1 is to be held, as standing up, by a retainer 3 which stands on a work-delivery box or a palette for conveying base tubes 1.
The chuck 5 in FIG. 2 is generally called an air picker or the like. More specifically, the chuck 5 has a balloon-like expandable body made of an elastic material such as rubber or the like, and is arranged to expand and contract by putting air in and out from this expandable body such that the base tube 1 is picked at the inner peripheral surface thereof. A chuck of other type may also be used. For example, as shown in FIG. 3, there may be used a link-type chuck 8 having a radially expandable arm 8a.
For picking a base tube 1, with the chuck 5 contracting in FIG. 2, the chuck-fixing unit 7 is lowered. While guided by the guide 4, the chuck 5 enters the inside of the base tube 1 from the upper end-thereof. Then, the chuck 5 is expanded to chuck the base tube 1 at the inner peripheral surface thereof. At this state, the chuck-fixing unit 7 is upwardly moved to lift the base tube 1. Then, the base tube 1 is moved to and placed on a machine for conducting another step, by the moving and placing machine having the chuck fixing unit 7. There are instances where instead of the base tube 1, a produced photoreceptor drum is moved and placed. Such base tube 1 or photoreceptor drum is generally called a work.
In picking, moving and placing works such as base tubes, work-delivery boxes or palettes for conveying base tubes or the like are successively fed with progress of the production. This produces positional differences between the moving and placing coordinates set in moving and placing machines and the axes of base tubes 1 or the like held by retainers 3, and such positional differences are not constant. If such positional differences are large, this results in defective movement and placement of works.
It is now supposed that, as shown in FIG. 4, the axes of the base tube 1 and the chuck 5 are positionally shifted by a length L. In such a case, even though the chuck 5 is lowered as shown by an arrow, the guide 4 comes in contact with the upper end of the base tube 1. This prevents the chuck 5 from being smoothly inserted. The chuck shaft 6 is securely fixed to the chuck-fixing unit 7. Accordingly, if the chuck 5 is lowered with the guide 4 being in contact with the base tube 1, this involves the likelihood that the base tube 1 is thrown down or crushed at its upper end.
More specifically, the retainer 3 comprises a column-like member upwardly extending from a palette 10 and its upper end is pointed in a tapering manner as shown in FIG. 5. The retainer 3 has an outer diameter determined according to the inner diameter of the base tube 1 such that the retainer 3 is fitted to the base tube 1 with a predetermined gap provided therebetween. For example, there are instances where for a base tube 1 having an inner diameter of 14 mm, there can theoretically be allowed only a difference of 4.388 mm between the axes of the upper end of the base tube 1 and the retainer 3, as shown in FIG. 5. If there is present a difference between the axes of the retainer 3 and the chuck 5 more than 4.388 mm, the retainer 3 probably rubs against the base tube 1 when the same is picked. Thus, there is a possibility of the base tube 1 being damaged or defectively moved and placed.